The course provides an introduction to a range of theories of bilingualism and how bilinguals make use of their languages across a range of setting and societies. It explores the issues from a range of perspectives, such as different types and degrees of bilingualism, the different roles played by each language in bilingual societies, the properties of bilingual speech, the bilingual brain, and the educational and other social policy for bilingualism. A key interest is also the ways in which theoretical stances inform our understanding of bilingualism and social policy, and the ways in which research into bilingualism can help inform wider theories of language acquisition, processing and use.